linux-kernel - Re: Follow-up on Linux-kernel code accessibility

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Message-ID: <159ec19f-0d82-4111-aac8-dfe684d6a640@paulmck-laptop>
Date: Fri, 26 Dec 2025 10:36:08 -0800
From: "Paul E. McKenney" <paulmck@...nel.org>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: Sasha Levin <sashal@...nel.org>, Theodore Tso <tytso@....edu>,
	Julia Lawall <julia.lawall@...ia.fr>,
	Gabriele Paoloni <gpaoloni@...hat.com>,
	Kate Stewart <kstewart@...uxfoundation.org>,
	Chuck Wolber <chuckwolber@...il.com>,
	Dmitry Vyukov <dvyukov@...gle.com>,
	Mark Rutland <mark.rutland@....com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
	Shuah Khan <skhan@...uxfoundation.org>, Chris Mason <clm@...a.com>,
	linux-kernel@...r.kernel.org
Subject: Re: Follow-up on Linux-kernel code accessibility

On Fri, Dec 26, 2025 at 11:51:36AM -0500, Steven Rostedt wrote:
> On Thu, 25 Dec 2025 10:18:20 -0800
> "Paul E. McKenney" <paulmck@...nel.org> wrote:
> 
> > > I'm not sure what you mean by "walkthroughs". AI can help give a general
> > > idea on code, but it still needs the author of the code to verify it.  
> > 
> > So let's kill two birds with one stone.  Let's arrange a walkthrough
> > of this code (starting from its calling function rcu_gp_kthread() some
> > time after the new year.  That will show you how a walkthrough works
> > (or at least one walkthrough method) and also answer your questions
> > about the variable "j".
> 
> Sure, I'll be up for that.

Sounds good!  Any particularly good/bad times for you?

> > > There's a bit of magical manipulation of "j" that I have no idea why it's
> > > doing that. ;-)  
> > 
> > Back in the old days, I used to put inline comments on local variables,
> > but this practice did not spark joy in the Linux kernel community back
> > in the very early 2000s.
> 
> Matters how much comments that was I guess. And how useful they were.
> Today, I believe people want comments. The kernel is much more complex
> today then it was back in the early 2000s.

Here are three examples:

o	Comment restricted to the remainder of the line.

o	Comment restricted to the remainder of the line, but the
	initialization was moved to executable code to make more room.

o	Comment extends for multiple lines.

> > So another question for our walkthrough:  Should this practice be
> > introduced into the Linux kernel?
> 
> I can't answer that until after the walkthrough ;-)

Well, you *could* answer, but you just might not be all that confident
in your answer.  You could build confidence in the meantime by looking
at other examples and asking yourself whether such a comment would
be helpful.  ;-)

> > > I would love if Julia or Gabriele came up with some specification for that
> > > function.  
> > 
> > Sounds like a worthy challenge to me!  Me, I would open it up to all
> > comers, but I was clearly willing to give Julia and Gabriele a one-day
> > head start, even if it was rather inconveniently timed.  ;-)
> 
> I'll let them speak for themselves.

Fair enough!

							Thanx, Paul